A doubly negatively ionized oxygen atom $(($:$m=2\mathrm{.}7{10}^{-26}(kg),q=-2e\}$ has an initial horizontal velocity of $4\mathrm{.}6{10}^4\frac{m}{s}.$ It enters the gap between the plates of a parallelplate capacitor. The capacitor is connected to a $1000-V$ power supply, as shown. Each plate has an area of $25c{m}^2,$ and the separation distance of the plates is $3\mathrm{.}3$ mm $.$ External Helmholtz coils provide a uniform magnetic field into the page of magnitude $1\mathrm{.}5$ T $.$

Determine the magnitude and direction $($up or down$)$ of the atom's acceleration $($at the instant when it is moving horizontally.$)$ Include a force diagram. Hint: ignoring gravity, two forces act on the charge.